Biosensors are devices which can convert the concentration of a single chemical analyte in a complex system by using various biological materials (e.g., cells, enzymes, tissues) into detection signals (e.g., electricity, sound, light, heat) that can be analyzed and processed. Nowadays, various biosensors have been developed to analyze various analytes. Among the various biosensors, electrochemical enzyme biosensors which can convert the concentration of an analyte into an electrical signal by using enzymes gain the most attraction. The primary form of these electrochemical enzyme biosensors is amperometry glucose sensor which is of great significance to diabetics, especially in usage of continuous monitoring of blood glucose.
Nowadays, a lot of research work about implantable glucose biosensors has been conducted. Implantable glucose biosensors are used to monitor the glucose concentration of diabetics. In order to monitor the glucose concentration, an implantable glucose biosensor usually has an electrode coated with an enzyme. The enzyme used may be glucose oxidase (GOx). In the implantable glucose biosensor, the glucose oxidase reacts with glucose, which will produce a substance that can be detected by the electrode.
The principle reactions of the implantable glucose biosensor are as follows.

The critical factor of an enzyme biosensor with stableness and high sensitivity lies in that the output signal of the enzyme biosensor depends only on the analyte to be detected, and may not be influenced by the other substances and corresponding dynamic control factors (e.g., diffusion). The above recited reaction formulas clearly demonstrate the challenges that the implantable glucose biosensor is facing. In order to maximize the output current, the oxygen must be diffused as much as possible, so that volume of the oxygen on the reaction interface can be adequate. If there is no enough oxygen for the reaction of glucose oxidase and the glucose, the output current will be affected by the oxygen concentration rather than be proportional to glucose concentration. That is, in order to ensure the applicability of these kinds of glucose biosensors, glucose must be a limiting reagent. In other words, the oxygen concentration should be far more than the glucose concentration. It means necessary measures are required to increase the oxygen concentration and to reduce the glucose concentration. Or else, a biosensor without oxygen consumption is desired.
The main problem in the usage of glucose biosensors is that the ratio of the glucose concentration to the oxygen concentration in human bodies is opposite to the above recited optimum concentration condition for a biosensor. The glucose concentration in diabetics may range from 2 mM to 30 mM (36˜540 mg/dL), and the typical oxygen concentration in tissues may range from 0.02 to 2 mM (Fischer, A. Hidde, H. vonWoedtke, K. Rebrin, and P. Abel, Biomed. Biochim. Acta. 1989, Vol. 48, pp. 965-971). The concentration ratio in diabetics will result in that the biosensor is not sensitive to minor changes in glucose concentration. The above recited main problem is generally called “oxygen starvation”.
In the last decade, many approaches have been tried to solve the problem of oxygen starvation. The most simple and direct approach is to use a polymer film outside the biosensor. The polymer film has good oxygen permeability, and can regulate the permeance of glucose. The polymer film also has good physical stability and strength, certain adhesion, good biocompatibility and good compatibility with the enzyme used in biosensors. Based on this strategy, people have successfully manufactured a variety of homogeneous or heterogeneous polymer film materials, among which the most prominent material is organosilicone compound. Organosilicone compound is also the main material disclosed in the present disclosure.
In order to be used in vivo, these implantable glucose biosensors should be easy to install and remove, small in volume, safe, nontoxic, accurate, stable and sensitive. In order to meet the safety requirements, the materials of the implantable glucose biosensors must be nontoxic, indissoluble, indiffusible and good in biocompatibility. In order to be used in vivo for a long time, the materials of the implantable glucose biosensors must also be stable enough to maintain their shapes and performance after being soaked in the body fluid for a long time.